This invention relates generally to the field of spray booths, and in particular to spray booths which minimize the travel of particulate across on object being sprayed.
Many spray booths attempt to provide a clean environment to facilitate the spray of a material onto an object, such as the spray of paint or a clear coat finish onto an automobile. Such spray booths are configured to flow air through the interior of the booth to remove particulate, such as overspray, from the interior so that a smooth finish may be provided on the object. One technique is to use a cross flow of air which passes horizontally through the spray booth. Although relatively easy to achieve, such a techniques moves any overspray along the length of the object before being exhausted from the booth.
In an attempt to minimize travel of the overspray along the length of the object, some spray booths utilize a down draft where the air flows from the ceiling to the floor. A pit is incorporated into the floor to exhaust the air. Construction of such a pit can be expensive, especially if the spray booth is constructed over a concrete floor. Some attempts have been made to provide a hybrid between the horizontal flow design and the down draft design by flowing the air cross wise or diagonally through the booth. However, even with this design, the overspray is moved diagonally across the object.
Another disadvantage of conventional prior art spray booths is that they often require a significant amount of space. For example, fans, heaters, filters, and the like are often held within a separate module located adjacent the main spray booth housing. As such, the number of spray booths that may be located within a given space is limited.
Hence, the invention provides spray booths and techniques that are configured to minimize the travel of any particulate or overspray along the object being sprayed. The invention also provides spray booths that are cost effective and space effective, thereby making them commercially attractive.
The invention provides exemplary spray booths and methods for their use. In one embodiment, a spray booth comprises a housing that is constructed of a ceiling and a set of walls that each have a bottom end and a top end. The walls and the ceiling define an interior into which one or more objects that are to be sprayed may be placed. An air intake is incorporated into the ceiling, and an exhaust outlet is provided near the bottom end of one of the walls. A circulation system is employed to introduce air into the interior through the intake and to exhaust air through the outlet. Further, the air intake is configured to produce an airflow gradient within the interior such that the flow rate decreases in a direction toward the outlet. In this way, the airflow through the interior is flowed in a generally downward direction to minimize the travel of overspray or other particulate along the object. Further, by positioning the exhaust outlet near the bottom end, a near downdraft may be created without the creation of a pit, thereby reducing the cost of the spray booth.
In one aspect, the intake comprises a plurality of flow plates that each have different densities and/or sizes of openings to produce the gradient. For example, the flow plates which are furthest spaced from the outlet may include a higher density of openings so that greater airflow is achieved at this location. Alternatively, the intake may initially be generally open to the interior to provide the greatest flow, followed by one or more flow plates with the same or different densities of openings to produce the gradient. In another aspect, the housing has a front end and a rear end, and the intake is located at the front end and the outlet is located at the back end. In this way, the airflow is greatest at the ceiling level at the front end and decreases in the direction toward the back end.
In one particular aspect, the circulation system comprises at least one intake fan and at least one exhaust fan. Conveniently, the intake fan may be disposed within the ceiling to minimize the size of the spray booth. In another aspect, a heater may also be disposed in the ceiling upstream from the intake fan, thereby further reducing the overall size of the spray booth. In yet another aspect, a filter material may be disposed above the flow plates to filter the air prior to entry into the interior.
In still another aspect, a filter tower may be vertically positioned over the outlet so as to form one of the sides of the spray booth. The filter tower may include a set of generally vertically oriented filters. Such a configuration may be used to further reduce the overall size of the spray booth by incorporating the outlet and the outlet filters in a side of the spray booth. In another aspect, the spray booth may include an outlet duct, with the exhaust fan being positioned between the filter tower and the outlet duct, thereby further minimizing the size of the spray booth.
To further integrate the components of the spray booth into a single housing, the spray booth may include an inlet duct extending vertically from the ceiling. Further, a wrap around duct may be positioned between the inlet duct and the air intake, with the wrap around duct extending around a periphery of the ceiling. Still further, the ceiling may include a plenum to distribute intake air to the air intake.
The invention further provides a method for spraying an object. According to the method, a spray booth is provided that comprises a housing having a ceiling and a set of walls that each have a bottom end and a top end. Further, the walls and the ceiling define an interior. An air intake is incorporated into the ceiling and an exhaust outlet is disposed near the bottom end of one of the walls. Air is passed into the interior through the intake such that an airflow gradient is produced within the interior. The gradient is such that the flow rate decreases in a direction toward the outlet where the air is exhausted from the interior. In this way, the air passes through the interior in a generally downward direction. While the air is flowing through the interior, an object that is disposed within the interior is sprayed with a material with any particular or overspray being drawn down to the floor and then across to the outlet to minimize its travel along the object.
In one aspect, the intake comprises a plenum and a set of flow plates having different densities of openings. With such a configuration, the air is passed into the plenum to produce the airflow gradient within the interior. In another step, the air is filtered prior to passing into the interior. Optionally, the air may also be heated prior to entry into the interior.
In one step of the method, the air may be forced into the interior using an intake fan. In another aspect, the air is filtered after exiting through the exhaust outlet. In still another aspect, the object comprises an automobile that is sprayed with paint or an overcoat.